Question from Kathy:
I love your book and use it as my garden bible.
I have a new problem and do not know what to do. I live on top of a steep hillside and have been here for 34 yrs. I have never had a mudslide. However, the hillside is in three levels and the bottom one had a some mudslide last winter. It was covered with the old heavy ice plant and the woman who lives across the street from my hill started pulling it out and planted red apple and some nasturtiums as she didn’t like the weeds in between the ice plant. Now I need to know how to fix this problem.
What is the best and toughest ground cover ?
I live in Rancho Palos Verdes. The slide is about 3 feet deep by about 4′ wide at the top and a narrow 9′ down to the street . It has thick red apple on one side and scattered old ice plant on the other side. Thank you so much
Answer from Pat:
Thanks for kind comment. Below are a lot of ways to fix a steep bank. I think I was considering a larger space than you actually have, but I have given you so much to chose from you can make it fit your needs. Also this advice may help others who read this site.
As you undoubtedly know landslides on the Palos Verdes Peninsula can be a serious matter since they might signal a problem with an entire strata of wet adobe soil slipping down over a harder layer of soil below. This kind of slide can happen when the “tow” of a hillside has been unwisely bulldozed or cut into. It might be wise for you to contact your UC Extension Home Horticultural Advisor, Department of Agriculture, or your local city officials before trying to do anything to correct the slide so you can first make sure there is no serious slippage problem in this case. In many cases in the past mudslides have endangered houses or even lives, though yours sounds smaller in scope than were those.
Once you have determined that this is not a widespread or potentially dangerous situation, then you can undertake some steps to try to correct the problem. First, ice plant is seldom a good solution for a very steep bank, since it can actually pull a bank down by its own weight. Nonetheless if it is growing there already and holding a bank it’s unwise to pull it out as your neighbor did since this can make the whole bank slide as happened in this case. A wiser way to make a change is to cut the ice plant short and leave the roots in place, then plant right through it. The roots will continue to hold the bank while the new plants take over. It’s too bad your neighbor didn’t know of this old-timers trick, a common practice in California gardens fifty or sixty years ago when people with new homes covered banks with ice plant quickly to hold them through winter rain then soon upgraded to something better.
Also, red apple ice plant is not a very good solution for steep banks since it needs a lot of water and calcium nitrate fertilizer to stay green. It’s far better to plant something more environmentally responsible. When trying to plant a bank for the purpose of stabilizing slipping soil, the very best way is to plant a mix of deeper- rooted larger plants along with shorter-rooted ground covers to cover the ground between them to hold the ground as the larger plants are getting going. Examples of shorter rooted ground covers are gazania or arctotis. Then you could dot such plants as shrubby bougainvilleas all over the bank, along with something like ceonothus ‘Concha’. I recommend bougainvilleas as one of the better plants for such an area. They will grow on a drip system and grab deeply into the soil. Once fully established they become very drought-resistant and you get a lot of bang for the buck. Another fairly deep-rooted bank cover plant is Acacia redolens ‘Desert Carpet’ or ‘Low Boy’. This too is very drought-resistant once established. Lantana montevidensis is hugely colorful with lavender flowers almost year round and also very drought-resistant, easy to grow and good on banks. Finally consider blue plumbago. For a gang busters combination on a bank and drought-resistant year-round color, plan yellow trailing gazanias to cover the ground, then use an equal number of the the following plants to send down deep roots and hold the soil: Bougainvillea ‘La Jolla’, Plumbago ‘Royal Robe’, and Lantana ‘Radiation’.
Another way to go and perhaps more exciting, but best planted in November: You could do the whole thing with native plants. You might try toyon or Calfornia holly (Heteromeles arbutifolia ) at the bottom of the slope. (Get the one from Catalina that has bigger berries.) For a native shrub requiring no water whatsoever in summer, plant flannel bush (Fremontedendron ‘California Glory’.) Or, for a compact one, try F. ‘Dara’s Gold’. Plant this next to ceonothus for a great color combination blooming at the same time in spring. I think natives are probably the way to go with this slope but you could get a ground cover going first to hold everything until fall. Matilija poppy (Romneya coulteri) is a great way to grab a bank but not a good time to plant now. I planted three of these last November and they are all growing and blooming. All natives are best planted in November but it would be all right to cover the bank now with some native ground covers though perhaps not California perfume (Ribes viburnifolium)—great on banks but might not survive planting now. But bear berry (Arctostaphylos urva-ursi) or coyote bush (Bacharis pilularis) I think might mostly survive along the coast even if planted now since we’re having cooler than usual weather, and then plant the bigger things in fall.
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